1. Field of the Invention
The present invention relates to movable body drive methods and movable body drive systems, pattern formation methods and pattern formation apparatuses, and device manufacturing methods, and more particularly, to a movable body drive method and a movable body drive system that drive a movable body along a predetermined plane, a pattern formation method using the movable body drive method and a pattern formation apparatus equipped with the movable body drive system, and a device manufacturing method using the pattern formation method.
2. Description of the Background Art
Conventionally, in a lithography process for manufacturing microdevices (electron devices and the like) such as semiconductor devices and liquid crystal display devices, exposure apparatuses such as a projection exposure apparatus by a step-and-repeat method (a so-called stepper) and a projection exposure apparatus by a step-and-scan method (a so-called scanning stepper (which is also called a scanner)) are relatively frequently used.
In this kind of exposure apparatus, in order to transfer a pattern of a reticle (or a mask) to a plurality of shot areas on a substrate such as a wafer or a glass plate (hereinafter, generally referred to as a wafer), a wafer stage that holds the wafer is driven in two-dimensional directions by, for example, a linear motor and the like. Position measurement of the wafer stage or the like is generally performed using a laser interferometer whose stability of measurement values is good for over a long period and which has a high resolution.
However, requirements for a higher-precision position control performance of the stage are increasing due to finer patterns that accompany higher integration of semiconductor devices, and now, short-term variation of measurement values caused by air fluctuation generated due to temperature change or temperature gradient of the atmosphere on the beam path of the laser interferometer has come to occupy a large percentage in the overlay budget.
Meanwhile, as a measurement device other than the laser interferometer used for position measurement of the stage, an encoder can be used, however, the encoder uses a scale, which lacks in mechanical long-term stability (drift of grating pitch, fixed position drift, thermal expansion and the like), and therefore the encoder has a drawback of lacking measurement value linearity and being inferior in long-term stability when compared with the laser interferometer.
In view of the drawbacks of the laser interferometer and the encoder described above, various proposals are being made of a device that measures the position of a stage using both a laser interferometer and an encoder (a position detection sensor which uses a diffraction grating) together (e.g. refer to U.S. Patent Application Publication No. 2002/0041380).
Further, the measurement resolution of the conventional encoder was inferior when compared with an interferometer. However, recently, an encoder which has a nearly equal or a better measurement resolution to/than a laser interferometer has appeared (for example, refer to U.S. Patent Application Publication No. 2005/236558), and the technology to combine the laser interferometer and the encoder described above is beginning to gather attention.
For example, in the exposure apparatus, in the case of performing position measurement of a wafer stage on which a scale (a grating) is arranged using an encoder, in order to cover a broad movement range of the wafer stage, it is conceivable that a plurality of heads are placed at a predetermined interval within a two-dimensional plane. However, in the case of using the plurality of heads having such a placement, because the scale is placed on the upper surface of the wafer stage, for example, foreign materials such as particles can easily adhere to the surface of the scale, and in the case such foreign materials adhere to the scale, position measurement accuracy of the wafer stage by the encoder reduces, or the position measurement becomes difficult.